When we access the Internet on our phones — as more of us do every day — we expect to be able to go wherever we want, whenever we want.

But a terrible new service plan from MetroPCS — the fifth-largest U.S. mobile phone carrier — is the latest phone industry attack on Net Neutrality. The company is limiting users' ability to access certain websites and services, unless they pay extra for the privilege.

Customers purchasing the most expensive plan will have to pay extra to access Netflix, Skype or any website using “advanced HTML” on their phones.

Those with the cheapest data option won't be able to access any of these online services, except for YouTube -- despite its similar data usage.

It gets worse. MetroPCS’s plans disproportionately affect people of color and urban communities, whom the company recognizes as a major portion of its customer base, and who largely depend on mobile phones to access the Internet.2

There is a way that we can stop MetroPCS's discriminatory practices. Last month, the FCC adopted weak rules that leave mobile Internet users virtually unprotected from these types of abuses, with two big exceptions: They prohibit the blocking of websites and competing video and voice communication applications on mobile phones. Yet that’s exactly what MetroPCS is doing.

The FCC must now take action to protect the public and enforce these new rules. If the agency does nothing, we could see a domino effect in which larger carriers like AT&T and Verizon introduce their own forms of mobile blocking and discrimination. We can’t let that happen.